A magnetic recording medium comprising a non-magnetic support having thereon a single magnetic layer or plural magnetic layers containing ferromagnetic particles composed of acicular crystals such as .gamma.-Fe.sub.2 O.sub.3, Co-containing magnetic iron oxide or CrO.sub.2 dispersed in a binder is generally used as a magnetic recording medium for use in audio recording, video recording or computers (hereinafter referred to simply as "magnetic tape" in some cases).
Recently, however, higher density recording has been demanded for magnetic recording media, and much finer ferromagnetic particles than conventional ones have been used. Much higher recording has been necessary, particularly for a video tape, as recording wavelengths have shortened and track widths have narrowed, and thus a video tape using much finer ferromagnetic particles than conventional ones has been used.
If such more finely divided ferromagnetic particles (for example, ferromagnetic particles having the average length in the long axis of 0.45 .mu.m or less and a specific surface area (S.sub.BET) of 25 m.sup.2 /g or more) are used and if the surface of a magnetic layer can be made smooth, it is known that higher density recording can be realized and that electromagnetic characteristics can be improved. However, there is the problem that the dispersibility of finely granulated ferromagnetic particles is decreased, and, therefore, the use of finely granulated ferromagnetic particles is not always satisfactory. Recently, the dispersibility of finely granulated ferromagnetic particles has been fairly improved by using binders having a polar group or by improving the dispersing method, and thus excellent electromagnetic characteristics can be obtained.
On the other hand, when the surface of a magnetic layer is made smooth, the friction coefficient as a result of contact between a magnetic layer and a running system is increased while the video tape is running, whereby a magnetic layer is likely to be damaged or to peel apart from a support in a short period of use. Particularly in a video tape, a video head and a magnetic medium run at high speed while in contact each other, and, therefore, ferromagnetic particles are likely to drop off from the magnetic layer, resulting in head clogging of a magnetic head. Accordingly, an improvement in running properties of a magnetic layer of a video tape is necessary.
It has hithertofore been proposed that abrasive agents (hard particles) such as corundum, silicon carbide or chromium oxide be added to a magnetic layer in order to improve the running properties of a magnetic layer. When abrasive agents are added to a magnetic layer to improve the running properties of a magnetic layer, a large amount of the abrasive agents must be added to exhibit the desired abrasive effect. However, a large amount of the abrasive agents contained in the magnetic layer causes wear of a magnetic head, and prevents improving the electromagnetic characteristics resulting from smoothing a magnetic layer. Therefore, the addition of abrasive agents is not a desirable approach.
It has also been proposed in JP-A-60-205827 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application") and JP-A-60-98526 that a fatty acid or an ester of a fatty acid and an aliphatic alcohol be added to a magnetic layer as a lubricating agent to reduce the friction coefficient. However, such lubricating effects are not fully exhibited in a magnetic recording medium using finely granulated ferromagnetic particles in many cases.
Accordingly, comparatively excellent electromagnetic characteristics have come to be obtained, but it is difficult to simultaneously secure excellent running properties.